What is defined as the number of atoms surrounding an atom in a crystal lattice?

coordination number

Explanation:

Coordination number -

In a crystal lattice , the number of atoms that are surrounded to a particular atom , is referred to as the coordination number of the crystal.

In the field of crystallography and chemistry , it is also called the ligancy.

In coordination chemistry , the number of ligands attached to the central metal atom is also known as the coordination number of the coordination compound.

Hence, from the given statement of the question,

The correct term is coordination number.

- lead + phosphoric acid = hydrogen + lead(ii) phosphate

- calcium has greater affinity to bond with electron receptors than hydrogen does and hence, it has the ability to replace hydrogen in most of its compounds.

- lithium has 2 valence electrons in the product because it can make only 1 bond with hydrogen. beryllium has 4 valence electrons in the product because it can only make 2 bonds. it has fewer electrons than neon and can react with electron donors. each hydrogen has 2 valence electrons, the same as helium.

- the covalent bond formed between carbon and hydrogen is polar because carbon is more electronegative than hydrogen and it attracts the bonded electron pair closer to itself, thus giving hydrogen a partial positive charge.

- a hydrogen bond is a relatively weak bond that hydrogen atoms make with the electronegative atoms nitrogen, oxygen or fluorine.

so the best choice is a.) 2 calcium (ca) atoms